(06 Jul 2014, 10:40 am)Michael wrote Should work well within London
It will, because the technology is there to support such a move. Most of your travellers in London will have either a Oyster card or an ENCTS pass. Those there for a day trip will normally pay for a day ticket as part of their rail tickets. In the rare occasion anyone won't have either of the three, then they can pay by contactless payment from a debit/credit card.